Rails ignoring asset_host in production but not in development

Question

I have set in config/environments/production.rb

config.serve_static_files = false
config.assets.compile = false
config.action_controller.asset_host = ENV['CDN_URL']

I ran RAILS_ENV=production bundle exec rake assets:precompile and uploaded the assets folder to my assets server.

In my machine I can start a production server and it works fine. But when I upload to the production server (nginx + unicorn) the rails app keeps using a local path instead of the asset_host

<script src="/assets/application-e5b02395783a59feaf5a100d0e23806c3e2bd45296770ebac0fc756f8e1dfd53.js" data-turbolinks-track="true"></script>

How do I make it fetch the assets from asset_host ?

EDIT To explain better my problem

On remote host:

$ RAILS_ENV=production bundle exec rails console
Loading production environment (Rails 4.2.3)
irb(main):001:0> puts helper.javascript_include_tag 'application.js'
<script src="/assets/application-e5b02395783a59feaf5a100d0e23806c3e2bd45296770ebac0fc756f8e1dfd53.js"></script>
=> nil
irb(main):002:0>

On local machine:

$ RAILS_ENV=production bundle exec rails console
Loading production environment (Rails 4.2.3)
2.2.2 :001 > puts helper.javascript_include_tag 'application.js'
<script src="http://cdn.site.com/assets/application-e5b02395783a59feaf5a100d0e23806c3e2bd45296770ebac0fc756f8e1dfd53.js"></script>
 => nil
2.2.2 :002 >

Answer 1

Found the problem.

I'm using figaro to handle environment variables. Someone changed permissions on application.yml and EVN['CDN_URL'] was returning nil on production servers.